Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$120.94	4.322%	$126.167	$126.17	$126.15	$126.20
Purchase #2	$194.52	12.471%	$218.7786	$218.78	$218.80	$218.80
Purchase #3	$95.42	10.680%	$105.6109	$105.61	$105.60	$105.60
Purchase #4	$47.50	5.730%	$50.2218	$50.22	$50.20	$50.20
Purchase #5	$43.96	12.716%	$49.55	$49.55	$49.55	$49.60
Purchase #6	$68.39	13.300%	$77.4859	$77.49	$77.50	$77.50
Purchase #7	$115.79	6.742%	$123.5966	$123.60	$123.60	$123.60
7 purchase totals =	$686.52		$751.4108	$751.42	$751.40	$751.50